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What is the best (i.e. most energy efficient (has the least energy loss)) way to reduce 120 VAC to various DC charging levels for simultaneously smart charging: a 12V deep-cycle/starting battery, an 18V tool battery, 7 3.7V Li-ion cells, & up to 8 AA/AAA nimh cells that all charge independently of each other?

Note: I'd prefer to have/make one bench charging station that allows me to simply connect one or more batteries/cells to it, rather than having a power strip & a mess of AC adapters/converters.

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  • \$\begingroup\$ The most energy efficient way is to not use 120V ac and use a solar panel. However you may need to check what the carbon footprint is of the supplier supplying the solar cell. \$\endgroup\$ – Andy aka Sep 27 '15 at 22:51
  • \$\begingroup\$ While I agree that using a lower voltage (closer to the V needed for properly charging each rechargeable device) would be more efficient, the premise of the question is based on the most efficient way to convert utility power "120 VAC" to various DC charging voltages. \$\endgroup\$ – zeffur Sep 27 '15 at 22:59
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    \$\begingroup\$ You didn't say solar panels couldn't be used and it's free energy of course. Maybe show some research on what you have found out so far? I'll also add that your profile gives no indication of how expert you are so it's difficult to pitch an answer on that basis. \$\endgroup\$ – Andy aka Sep 27 '15 at 23:02
  • \$\begingroup\$ True, I didn't type solar panels couldn't be used, but the essence of my questions is about the efficiency of converting AC to DC for charging purposes. As for research, I have considered voltage dividers, linear regulators, & SMPS (switch mode power supplies) as possible circuits that would work, with SMPS being the most efficient. What I do not know is if there are any other more efficient methods available--which is what I was hoping someone with much more knowledge would provide for everyone's edification. \$\endgroup\$ – zeffur Sep 27 '15 at 23:05
  • \$\begingroup\$ SMPS every time \$\endgroup\$ – Andy aka Sep 27 '15 at 23:30
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If your application requires that 8 NiMH, or any other chemistry cells be charged separately, then you may have a common charging source, but the circuitry used to charge each cell must be devoted to serving only that cell.

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  • \$\begingroup\$ Agreed. Ideally, the base charger would be a small/light powerful box that could serve on the bench or under the hood of a vehicle. It would have power ports to connect a variety of rechargeable cells/batteries & user controls to set the max charge V, max charge A, and displays that show the current V, charging rate (A), & charge time. There system will be smart & shut off charging once the charge current drops below a predefined/user defined setting and a channel switcher to display charge info for each connected cell/battery. \$\endgroup\$ – zeffur Sep 29 '15 at 1:12
  • \$\begingroup\$ @zeffur: Pie in the sky. What you're asking for is a design for a system which which would, ostensibly, make you rich, but which you don't want to pay for. Why would anyone find that an attractive offer? \$\endgroup\$ – EM Fields Oct 2 '15 at 1:08
  • \$\begingroup\$ If "Pie in the sky." means that you think what I described is unrealistic, then I would have to disagree with you. What I described is essentially a smart charging console which is certainly feasible to design & build. As for 'a system which ... would making me rich", I think that's a big stretch too because I described the basic functions of my charging system idea already--so ANYONE with sufficient wherewithal could make it--so what I want isn't a secret or designed to make me rich. It's nice to know that you recognize a good idea when you see one, though. \$\endgroup\$ – zeffur Oct 2 '15 at 4:22
  • \$\begingroup\$ @zeffur: Saying that you want a flying carpet isn't exactly letting the cat out of the bag, and if you don't know how to design/build it, you can't really attest to the feasibility of the idea being changed from fiction to fact with any degree of authority. \$\endgroup\$ – EM Fields Oct 2 '15 at 9:14
  • \$\begingroup\$ Good thing I didn't mention anything about a flying carpet. Since all of the circuits exist today, it IS feasible to build a device with such capabilities. It will get built with or without your support. Thanks for your contributions thus far. \$\endgroup\$ – zeffur Oct 2 '15 at 9:22
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Although multi-chemistry charge solutions exist (typical device linked), they each have their own charge sequence requirements and charge power.

Some useful links:

Charging Lithium Ion, Charging NiMH, Charging Lead-Acid.

There are numerous articles available on each type. My point here is to support the other answer that each charge type should have its own port as you can usually only use the charge controller in one chemistry mode for a given design as it is nigh on impossible to detect precisely what you have just attached.

Note that multi-cell stacks may need cell balancing for many reasons, including safety.

HTH

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  • \$\begingroup\$ Your multi-chemistry link is the first answer to actually get to the essence of answering my question because it actually shows the efficiency of the charging system as > 87%. This is the kind of answers that I was hoping to see in response to my question: "This SMPS circuit design <online link inserted here> for LA batteries is 90% efficient." This new circuit design <online link inserted here> for li-ion cells/batteries 97% efficient." \$\endgroup\$ – zeffur Sep 29 '15 at 1:00
  • \$\begingroup\$ Ideally, the base charger would be a small/light powerful box that could serve on the bench or under the hood of a vehicle. It would have power ports to connect a variety of rechargeable cells/batteries & user controls to set the max charge V, max charge A, and displays that show the current V, charging rate (A), & charge time. There system will be smart & shut off charging once the charge current drops below a predefined/user defined setting and a channel switcher to display charge info for each connected cell/battery. \$\endgroup\$ – zeffur Sep 29 '15 at 1:08
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You have a bunch of batteries with different chemistries and different voltages. You won't find a smart charger that can do all of them.

The most sensible option is to hide all the messy wiring under the bench, and switch on each of the chargers as you need it.

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  • \$\begingroup\$ Agreed, however then I wouldn't learn much about making such a versatile charger (which will be next), right? \$\endgroup\$ – zeffur Sep 29 '15 at 0:39

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